Metallurgical apparatus



' Sept. '30, 1947.-

D. K. FERRIS METALLURGICAL APPARATUS Filed March 22, 1943 3 Sheets-Sheetl Steel Transform: Hon

IIL l INVENTOR.

BY M 1 I Sept 30, 1947. R 5

METALLURGICAL APPARATUS Filed March 22, 1943 5 Sheets-Sheet 2 INVENTOR.A 1- K. 7%.

Sept, 30, 1947. D. K. FERRIS METALLURGICAL APPARATUS 3 Sheets-Sheet 55Filed March 22, 1943 Patented Sept. 30, 1947 'UNITED STATES PATENTOFFICE 'METALL'URGICAL APPARATUS Donald K. Ferris, Dayton, Ohio,.assignor to General Motors Corporation, Dayton, Ohio, acorporationofDelaware Application March 22, 1943, Serial No. 480,005

.5 Claims.

This invention relates to metallurgical method and apparatus and moreparticularly to :the thermal hardening of steels, .alloys and the likein which the hardening is obtained by reason of the phenomenon ofcompound particle solution :and subsequent precipitation in the "metal;at the various appropriate temperatures so as to produce .a bainitecrystal-structure.

One object of the present invention is to provide an improved thermallyhardened carbon or .alloy steel product.

Another object of the present invention is to provide apparatus forthermally hardening masses of small articles Such as .latches, bolts,nuts, springs, and the like.

This invention constitutes an improvement :over the now well-knownmethod and apparatus set forth in the patent-to Bain et al., 1,924,099.The process and apparatus described in the above identified patent islimited to small sections of steel as explained in the recently issuedpatents to Elmdorf et al. 2,258,566 and Mayo .et .al. 2,289,138, whereasit is an object of this invention to thermally harden steels to agreater depth by modifying the process and apparatuslin the mannerexplained hereinafter.

While it has been common practice to agitate the quench liquid so as tomaintain uniform temperatures 'throughout th'e liquid and so as toprevent overheating or the liquid by the heated steel at the point wherethe steel enters the quench liquid, the rate of agitation formerlyprovided was not enough to materially effect the depth to which thesteel was converted into bainite. It is an object of this inventiontherefore to improve upon the quench treatment so as to cool the metalto be quenched to a greater depth within the required time. In order todo this the heatedquench liquid is agitated very violently the first fewseconds after'the hot metal has been dumped into the quench liquid.

A further object 10f this invention is to safeguard against improper.operation :of the -appa ratus.

A further object of this invention is to provide an improved means forproducing violent movement of a large quantity of'quenching liquid.

A still further object is to improve upon the direction of flow of thequenching liquid relative to the direction of movement of the articlesdischarged from the :furnace into the quenching liquid. 7

Another objectis to prevent the heated articles from contacting the .airwhile moving :irom the iurnaceinto thequenching liquid.

A further object is to provide means for preventing the small sizedparticles being treated from being carried away by the liquid.

Further objects and advantages of the present invention will be apparentfrom-the follow-- ing description, reference being had to theaccompanying drawings, wherein a preferred form of the present inventionis. clearlyishown.

Inthe drawings:

Fig.1 is an elevationa'lviewsomewhat diagram matic showing an apparatusembodying .my invention;

Fig. 2 is a plan view, with partsiloroken away, 0f the apparatus :shown:in Fig. 1;

Fig. 3 is --a sectional view taken on line of Fig. 2.;

Fig. 4 is a horizontalssectional view taken on line 4-4 of Fig. 3;

Fig.5 is .a fragmentary elevational view showing the apparatus forcontrolling the dumping of articles from the furnace into the quenchbath;

Fig. -6 is a vertical sectional view somewhat di- .agrammatic showingthe liquid agitating means and the path ofmovement of the quench-liquid;

Fig. 'lis aview similar-to Fig. Gshowing a modified formof liquidagitating means;

Fig. 8 15a fragmentary sectional view on an enlarged scale takenon'line'88 .of Fig. 2 showing the chute -latching mechanism; and i Fig.9 shows the 8 curve fora typical steel.

By heating apiece of steel to .a temperature of approximately 1500 F. ina hydrizing atmosphere the grain structure .of the steel will betransformed into austenite and by transferring the steel thus heated toa quench bath maintained somewhere between 300 F. and 1000 F. -the grainstructure of the :steel will be transformed into'bainite which comprisesgrains other than coarse pearlite or martensite. The temperature atwhich the quench liquid should be maintained depends upon the type ofsteel treated and the hardness desired. For most purposes temperaturesbetween 500 F. and 620 F. are preferable.

The general process of heat treating steel to transform austenite to'bainite is well known. Likewise, the thermal hardening time curves,commonly known as curves, are known for many typical commercial steels.A typical '8 :curve is shown in Fig. =9 wherein the line A has beenadded to illustrate a typical rate of tempera'bllre change :which willproduce bainite "and the line B hasbeenadded to'designate-a-rate ofchange which is too slow-to pass the nose temzperature'of the s'curveandtherefore too slowto 3 prevent the transformation into pearlite whichprecludes the transformation into bainite.

No special difficulty is experienced in quenching the outer surface ofthe articles in the required time but great difficulty has beenexperienced in cooling the inner portion of the articles within therequired time. Prior to my discovery it was considered thatthe maximumdiameter of a round piece of S. A. E. 1095 steel, for example, whichcould commercially be transformed into bainite by the Bain et a1. methodwas approximately A; inch Whereas I have found that by using asufficient amount of quenching liquid and by Violently agitating thequenching liquid, the maximum sections of this same type of steel whichmay be transformed into bainite is several times greater than wasformerly considered possible.

The quenching liquid used may be any one of 1 several different liquids.of 55% NaNOe plus 45% KNO2 is very effective and does not attack themetal being treated.

Referring now to the drawings wherein I have shown apparatus, forthermally hardening metals in accordance with my invention, referencenumeral l0 designates a conventional hydrizing furnace having a door 12through which the articles to be treated may be inserted into thefurnace for heating. While the furnace I0 is preferably suspended fromthe ceiling, any other means for mounting the furnace could be used.Reference numeral l4 designates an insulated tank having an internaldiameterof 4 feet and containing quenching liquidto a depth of 26inches. A chute i6 i provided for directing the articles to be hardenedfrom the furnace ID to the tank [4.

Within the tank I4 I have provided a revolving rack "3 having sixbasket-carrying sections which are supported from the main shaft 22 bymeans of the arms 24 and 25. The main shaft 22 is a hollow shaft whichis rotationally journaled in the top wall 26 of the tank M. The shaft 22carries a sprocket 30 at its upper end which is connected to the hand 32by means of a chain or the like 34. sprocket 32 is carried by the shaft36 which is provided with a hand crank 38. The cover 26 includes ahinged portion 2611 which may. be lifted so as to remove and replace thebaskets containing the heat treated articles.

The liquid within the tank [4 may be heated by means of a plurality ofelectrical heaters such as the strip heaters 40 which are uniformlyspaced around the periphery of the tank as shown. A thermostat 42projects into the tank through the cover 26 and serves to control thetemperature I have found a solution The operated sprocket V of thequench liquid in accordance with Wellknown practice.

A reciprocating shaft hollow of the shaft 22. shaped agitator 46 havinga 21 inch diameter at the base is secured to the shaft 44 as shown so asto reciprocate along with the shaft 44. A walking beam. 48 pivoted'at507 on the frame 52 has its one end 54 pivotally connected to the shaft44 and has its other end 56 pivotally connected to the connecting rod 58whereby reciprocation of the connecting 10d 58 causes a correspondingreciprocation .of the shaft 44. The lower end of the connecting rod 58is operated by means of an eccentric lilldriven by a motor 62 through areduction gear mechanism 64,

The motor 62 is preferablya two-speed motor designed to cause theagitator 46 to operate at 44 passes through the A substantially cone 300or more strokes per minute at its high speed and to operate at anywherefrom to 250 strokes per minute at low speed. I have found that byoperating the agitator 46 at 300 strokes per minute with a two inchstroke and a threequarter inch clearance between the agitator 46 and thebottom of the tub M, the liquid flows very rapidly in the directionindicated by the arrows in Fig. 6; Since the agitator'is required tohandle such a large volume of liquid at such a high velocity, a 7horsepower motor is used to operate the agitator. In view of the largeamount of power required to produce the necessary veloc- 'ity of theliquid, the agitator is operated at its high speed for only a short timeprior to the dumping of the heated metal and for only a short time aftereach batch of metal has been dumped. Tests indicate that if the agitatoris operated at a high speed for approximately one minute and at a slowspeed thereafter for approximately an hour before the metal is removedfrom .the liquid, the desired quenching takes place.

Since the velocity of the quench liquid differs in different locationsalong the path of the falling metal and since the velocity at any onepoint fluctuates due to the pulsations produced by the reciprocatingagitator, it is difiicult to state the exact velocity in terms of feetper minute above which the liquid must flow in order to materiallyincrease the depth to which transformation to bainite takes place. It isa simple matter, however, to determine when the velocity is high enoughby heat treating sample pieces of a given type of steel such as S. A. E.1095 steel and then checking the maximum section which is transformedinto bainite. Without adequate agitation of the liquid the maximumsection of S. A. E. 1095 steel which may be transformed is approximatelyone eighth of an inch whereas with agitation as provided by my apparatusthe maximum section which may be transformed is several times greater.

In Fig. 7 I have shown a modified agitator construction which isdesigned to concentrate the flow of quenching liquid in the onedirection. Thus by providing a tilted agitator such as the agitator 4601the velocity of the liquid at the point 68 is much greater than thevelocity of the liquid at 69. This being the case the velocity of theliquid at point 10 is much greater than the velocity at 12. By, virtueof this construction it is possible to obtain the equivalent of a jet ofliquid directed toward the incoming metal to be quenched. However, thevolume of liquid in the jet is very great whereby the heat given off bythe metal to be quenched is absorbed at a high rate. Referring toFigs. 6and 7 it will be noticed that the directional flow of the liquiddirectly beneath the chute I6 is such that it flows at right angles tothe .direction of movement to the metal dumped from the chute.

Inasmuch as the success of the quenching operation depends considerablyupon the velocity of the liquid striking the hot metal to be quenched itis desirable that the basket designated by the reference numeral 14 intowhich the hot metal is dumped be highly perforated so as not tomaterially restrict the flow'of liquid. The perforations 76 have beendiagrammatically represented in Fig. 8; Obviously the entire basket isprovided For certain purposes baskets simplify the disclosure somewhat,

anaaoes 5 whereas the rack would normally have a basket in each of thesections 20.

In order to make sure that the basket car-rying rack is properlypositioned so that there is a basket directly under the chute to receivethe metal articles dumped from the chute, I have provided a firstindexing means comprising a lever "I8 which is carried by the side wallof tub as shown at 80, Fig. 'i'an'd which engages the notches "8'2provide'don thebasket carrying racks 2'0. In addition tothe indexingmeans for properly positioningthe bas'ket-carryingrack, I have providedfurther means for preventing dumping material into'thequen'ch bath inthe event that no basket has been placed in the basket-carrying sectiondirectly bene'ath'the chute. As best shown in Figs. 1 and "8 the chuteI6 comprises an uppterfsection 'Bflwhic'h is secured directly to thefurna'ce'lfl and a'lowe'r portion 86 secured to the lever .88 by meansof the pins 90. The lever 88 is fulcrumed on the cover 26 by means ofthe fulcrum element 92. A latch element 95 is provided with a la't'chbliwhich is arranged to engage a stop '98 on the chute section '86 in theevent that a basket has not been placed in the rack section directlybeneath the chute. The element 94 is provided with a depending arm I06]which cams the latch 96 out of the path of the stop 98 when a basketmoves beneath the chute. As shown in Figs. 4 and 8 each basket isprovided with a projecting cam surface I02 which is arranged to engagethe arm 1'00 and move'it into the dotted line position when the basketis directly beneath the chute. In order to-facilitateremoval of thebaskets at the completion of the quenching operation each basket isprovided with handies 1 04 as shown in Fig. 8.

An interlock has alsobeen provided between the means for dumping the:hot metal from the furnace into the chute and the chute loweringmechanism. Referring to Fig. 5, reference numeral I06 designates ahandle which serves to dump the hot metal particles from the furnaceinto the chute. The handle I06 is .provided with a crosspiece I08 towhich opposite ends of a cable H are secured as shown in Fig. 5. Thecable I I0 is secured to the lever 88 at its outer end I I2 wherebymovement of the handle I06 tends to raise or lower the chute section 86.By virtue of this construction it is impossible to dump the heated metalfrom the furnace into the chute when there is no basket beneath thechute to cam the latch 96 away from the path of the stop 90. In thelower position of the chute element 88 the chute element 86 projectswithin the basket whereby the quench liquid flowing substantially atright angles to the outlet of the chute cannot prevent the fallingarticles from falling into the basket.

Since the success of the quenching operation depends upon the highliquid velocity it is important that the motor 62 be operating at itshighest speed for a short time before each batch of metal is dumped andfor a short time after each batch is dumped. I have provided means forpreventing the operation of the dumping lever I06 except at those timesWhen the motor 62 is operating at its high speed. As shown in Fig. Ihave provided a conventional time switch H6 which is used for timing themotor operation in accordance with well-known practice. By manuallypressing the time switch button M8, the motor speed control relay I20causes the motor B 'to b'e oper-a'ted at its full speed for the desiredlength of tinie. Shortly after depressing the button l 1-8 the relay I22is energized and this retracts the latch 124 which would otherwiseprevent operation of thelever I05. By virtue of this construction itbecomes necessary for the operator to first :depress the button -'I IBsoas to step up the speed of the motor and then wait a predeterminedlength of time for the latch I24 to be retracted before dumping theheated metal into the quench bath.

The time switch H5 is set to automatically deenergize the relay I20after a predetermined length of time depending upon the type of metalbeing treated, etc. Likewise, the time switch H 6 deenerg-i'zes therelay I22 after a predetermined length' of timewhioh may be set so as togive enough time to return the handle I05 to its full line position asshown in Fig. 5. Electricity is supplied to thetime switch H0 throughthe lines I30 whereas electricity is supplied to the motor 62 throughthe lines I32. Inasmuch as time switches of this type are well-known andinasmuch as the specific construction of the time switch does not enterinto this invention no further description thereof needs be given.

The temperature values, time values, etc., given herein have been givenfor purposes of illustration as it is apparent that these values may bevaried somewhat without departing from the spirit of my invention.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, as may come within the scope of the claims whichfollow. a

What is claimed is as follows:

1. Apparatus for thermally hardening steel comprising in combination, afurnace for heating said steel to a temperature at which the steel isconverted substantially fully to austenite, a receptacle adaptedtocontain a quench liquid, means for maintaining said liquid at atemperature below 1000 F. but above the temperature at which rapidformation of martensite is produced, means for agitating said liquid,means for dumping the steel from said furnace into said quench liquid,said means for agitating said liquid comprising a variable speedagitator, and interlocked means between said speed varying means and themeans for conveying the steel from said furnace into said quench liquidcomprising means for preventing heated steel from being dumped into saidliquid when said agitator is operated at a slow speed.

2. Apparatus for thermally hardening steel comprising in combination, afurnace, a quench liquid receptacle disposed substantially beneath saidfurnace, a chute for conveying heated articles from said furnace to saidreceptacle, basket holding means within said receptacle adapted toremovably support a basket beneath said chute, means for dumping heatedarticles from said furnace through said chute into said basket, meansfor preventing operation of said dumping means in the absence of abasket beneath said chute, means for agitating the quench liquid withinthe receptacle, variable speed means for operating said agitating means,and interlock means between said variable speed means and said dumpingmean-s comprising means for preventing operation of said dumping meanswhen said agitator is operated at slow speed.

3. Apparatus for thermally hardening steel comprising in combination, afurnace for heating said steel to a temperature at which the steel isconverted substantially fully to austenite, a receptacle, adapted tocontain a quench liquid, means for maintaining said liquid at atemperature below 1000" F. but above the temperature at which rapidformation of martensite is produced, means for agitating said liquid,means for dumping the steel from said furnace into said quench liquid,and interlocked means between said agitating means and the means forconveying the steel from said furnace into said quench liquid comprisingmeans for preventing heated steel from being dumped into said liquidwhen said agitator is inefiective to properly quench said steel.

4. Apparatus for thermally hardening steel comprising in combination, afurnace, a quench liquid receptacle disposed substantially beneath saidfurnace, a chute for conveying heated articles from said furnace to saidreceptacle, basket holding means within said receptacle adapted toremovably support a. basket beneath said chute, means for dumping heatedarticles from said furnace through said chute into said basket, meansfor preventing operation of said dumping means in the absence of abasket beneath said chute, means for agitating the quench liquid withinthe receptacle, and interlock means between said agitating means andsaid dumping means comprising means for preventing operation of saiddumping means when said agitator is ineifective.

5. Apparatus for thermally hardening metal comprising in combination, afurnace for heating said metal, a, receptacle adapted to contain aquench liquid, means for agitating said liquid,

means for dumping the metal from said furnace into said quench liquid,and interlock means between said agitating means and the means forconveying the metal from said furnace into said quench liquid comprisingmeans for preventing heated metal from being dumped into said liquidwhen said agitator is inefiective to properly quench said metal.

DONALD K. FERRIS.

file of this patent:

5 UNITED STATES PATENTS Number Name Date 571,678 Myers Nov. 17, 1896636,005 Schulze Oct. 31, 1899 687,716 Bennett Dec. 3, 1901 723,977Barney Mar. 31, 1903 1,350,697 Bock Aug. 24, 1920 1,388,575 KenworthyAug. 23, 1921 1,924,099 Bain et al Aug. 29, 1933 2,040,111 Thornberg May12, 1936 2,060,645 Suppiger et al Nov. 10, 1936 2,061,563 Chambers et a1Nov. 24, 1936 2,151,146 Petry Mar. 21, 1939 2,246,675 Gronemeyer June24, 1941 ,379 Statz et al Jan. 27, 1942 2,280,470 Bridges Apr. 21, 19422,290,103 Hohl et a1 July 14, 1942 2,294,829 Bridges et a]. Sept. 1,1942 2,322,777 Purnell June 29, 1943 2,341,766 Fox Feb. 15, 19442,364,565 Stubbs Dec. 5, 1944 FOREIGN PATENTS Number Country Date142,671 Great Britain May 13, 1920 489,970 Germany Jan. 24, 1930 OTHERREFERENCES Grossman, re- Metals, Cleve-

